Electromagnetic well logging

QuickField simulation example

This simulation example is prepared by Professor James R. Claycomb as a part of the webinar Geophysical and Astrophysical Simulations in QuickField.
Excitation and receiver coils are translated through a borehole passing through geological formations with different conductivity.

Problem Type
Axisymmetric problem of AC magnetics.

Geometry

Given
AC current in primary coil is 1 A, frequency f =1 MHz.

Task
Calculate the secondary coil induced voltage.

Solution
Coils cross-section and wire dimensions are much smaller than the coil diameter and the distance between coils. So the primary coil cross-section is represented by an infinitively small vertex with a current value specified.
The induced voltage in the secondary coil is proportional to the magnetic flux linked with the coil. So the secondary coil is not included in the model, instead the flux through the would be coil area is measured. The voltage can be calculated as 2πf * number of turns * magnetic flux.
A set of problems is simulated with the coils assembly placed at different depths of the well. The set of QuickField problems is automatically generated by the Label Mover tool.

Results
Current density distribution at some specific coil depths is shown on the picture. The magnetic flux linked with the secondary plot vs coil position is shown on the plot. It clearly shows the increase of magnetic flux near the underground salt water region.

• Video: Electromagnetic well logging
  
• Download simulation files (files may be viewed using any QuickField Edition).